Means for and method of coating the interior of tubes



March 17, 1931. I c, MQORE 1,796,338

MEANS FOR AND METHOD OF COATING THE INTERIOR OF TUBES Filed Feb. 8. 1929 3 Sheets-Sheet l c. F. MOORE March 17, 1931.

MEANS FOR AND METHOD OF COATING THE INTERIOR OF TUBES 3 Sheets-Sheet 2 Filed Feb. 8. 1929 C. F. MOORE March 17, 1931.

MEANS FOR AND METHOD OF COATING THE INTERIOR OF TUBES Filed Feb. 8. 192's: s Sheets--Sheet 721/62? for" C/garles Z'T/Yoore Patented Mar. 17, 1931 UNITED STATES PATENT OFFICE CHARLES F. MOORE, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO THE DAMPNEY COM- PANY OF AIMERICA. 01 BOSTON. MASSACHUSETTS, A CORPORATION OF MASSACHU- SETTS MEANS FOR AND METHOD COATING THE INTERIOR OF TUBES Application filed February 8, 1929. Serial No. 338,370.

This invention relates to the coating of tubes and similar objects with a protective preparation. and more particularly to means for and a method of coating the interior of tubes.

It is known to apply a coating of a protcc' tive composition to the interior surfaces of tubes by means of brushes which are rotated and are moved through the tubes. This means of coating the interior of the tubes is satisfactory for tubes of one and one-half inches or more in diameter. but is not practical for smaller tubes due to the difficulty of constructing suitable brushes sufficiently small to be used to advantage in tubes of relatively small diameter.

There are many types of power plant equipment having steel. brass or bronze tubes of less thanone and one-half inches interior diameter. such as superheater tubes, condenser tubes. etc. The tubes of surface condensers commonly have an interior diameter of from seven-eighths of an inchto one-half an inch. The tubes of larger diameter in a power plant. for instance, such as the boiler tubes. can be readily coated by brushes in the manner referred to. The tubes of smaller diameters. such as the condenser tubes and superheater tubes. cannot be interiorly coated to advantage by the use of brushes and one of the main objects of my present invention is to provide means whereby these smaller tubes can be provided on their interior surfaces with a protective coating. A further object is to provide means and a method whereby either straight or curved tubes of relatively small diameter can have a protective coating uniformly distributed over the inner surfaces thereof. Another object is to provide means and a method capable of high speed operation, such means and method rendering it possible to coat the inner surfaces of tubes much faster than is possible by the us of rotating brushes passed through the tubes. Further objects and advantages will appear from the detailed description In the drawings:

Figure 1 is an elevation, partly broken away and in section, of a gun used in the practical application of my method;

Figure 2 is a section taken substantially on the line 22 of Figure 1;

Figure 3 is an elevation of a coating plug used in practicing my method;

Figure 4 is an elevation of a modified form of plug;

Figure 5 is an elevation of a second modified form of plug;

Figure 6 is an elevation of a third modified form of plug;

Fi ure 7 is an end view of the plug of Fig ure (7, taken from the nose end thereof;

Figure 8 is an elevation of a fourth modified form of plug;

Figure 9 is a longitudinal sectional view through a tube illustrating the positioning of the reservoir plug therein, this being the first step in practicing my method;

Figure 10 illustrates the second step of the method in which the reservoir plugis properly positioned within the tube by the, gage rod. the gage rod being shown in elevation and the tube in axial section;

Figure 11 illustrates the third step of the method in which the coating preparation is placed in the tube by a suitable gun, the gun being shown in elevation and the tube in axial section;

Figure 12 illustrates the fourth step in the method, in which the coating plug is inserted into the end of the tube, this plug being shown in elevation and the tube in axial section;

Fi gu res 13. 14 and 15 illustrate the fifth step in my method. in which the coating plug is projected through the tube by air admitted between the outer end of the plug and the adjacent end of the tube from an air gun, these views illustrating the successive positions of the coating tube relative to the reserthe tube and forms 'a snug closure therewith,

being of cylindrical form. The plug 1 is then positioned accurately in tube 2 by means of the gage rod 3 having end heads 4 and 5 of different diameters for use with different sizes of tubes. A stop collar 6 is adjustably secured on rod 3 by a thumb screw 7. The

position of plug 1 within the tube 2 will depend upon the interior diameter of the tube and the length thereof as well as, to some extent, upon whether the interior surface of the tube is to be provided with a thin or a thick coating of the protective composition.

After the plug 1 has been positioned within the tube the material or composition 0- with which the interior surface of the tube is to be coated is placed in the tube between plug 1 and the adjacent end of the tube, by means of a. suitable gun 8, as in Figure 11. This gun is, in general, of known construction and comprises a barrel 1 having end heads 10 and 11 screwed or otherwise suitably secured upon the ends of the barrel so as to be readily removable therefrom. A discharge nozzle 12 is secured in head 11 and receives a stopper 13 which is mounted upon the nozzle and is held tightly in position there-on by friction. This stopper 13 is of frusto-conical shape, tapering toward the discharge end of the nozzle. The stopper 13 is provided, in its outer surface, with a groove 14 extending from end to end thereof. When the stopper 13 is inserted into the end of tube 2 so as to close the same, as in Figure 11, groove 14 provides an air vent or escape to facilitate flow into the tube of the composition 1.: discharged from the nozzle 12. I also preferably provide a stop member or collar 15 adjustably secured by a set screw 16 on a threaded rod 17 which screws through head 10 and is secured, at its inner end, to piston 18 operating in the barrel. A jam nut 19 is threaded upon screw 16 and acts to hold the screw against casual displacement in a known manner. A suitable handle 20 is secured on the outer end of rod 17 for rotating the same. By providing the stop collar 15 the movement of piston 18 toward head 10 is positively limited and by properly setting this collar upon rod 17 a measured quantity of coating material or composition 0 is placed in the barrel of the gun and is discharged through nozzle 12 into the tube 2.

This is advantageous as assuring the proper quantity of composition for coating the interior of the tube while eliminating waste due to an excess quantity of composition being placed in the tube. The proper setting of the collar 15 upon rod 17 for a given interior diameter and length of tube can be determined by measurement of the distance between the piston and the collar, this distance being known and obtained from a table or suitable formula.

After the proper quantity of coating material or composition 0 has been placed in the tube the gun 8 is removed and a plug 21, which I term a coating plug, is inserted in the end of the tube, as in Figure 12. This plug has a cylindrical body and a blunt rounded nose 21a which tapers toward the reservoir plug 1. The plug 21 is preferably formed of rubber or other highly elastic and readily yieldable material, and is provided in its base wit-h a recess 22 of appreciable depth and area. The rubber used in the plug is preferably soft rubber and the reservoir plug 1 is also preferably formed of soft rubber.

\Vith the plug 21 in the position of Figure 12, the two plugs and the intervening portion of the tube-2 provide a reservoir for containing the coating material a. The coating plug, together with the reservoir plug 1 and a.

the coating material 0 confined between the two plugs is projected or shot through the tube 2 by means of an air gun 23, of known type, having a valve 24 controlled by a valve lever 25.

This air gun is connected by a conduit or hose 2 6 to a suitable source of compressed air. A tapered cap 27a of rubber or other suitable compressible material is suitably secured about the outer end portion of nozzle 27 of the air gun 23. This cap 270. fits into the end of tube 2 so as to form an air-tight closure therewith, the insertion of the end of the nozzle into the tube serving to move the coating plug 21 inwardly into the tube a short distance, as in Figure 13, with the tip of the nozzle disposed in recess llpon opening of the valve of the air gun 23, air is admitted to the tube under suitable pressure, approximately ninety pounds pressure to the square inch being ordinarily used. This projects the coating plug 21 through the tube toward reservoir plug 1. Due to the taper of nose 21a, the material or composition 0, which is in the form of a liquid, is caused to spread outwardly radially of the tube about the nose of the coating plug the body of which is approximately one oncs hundredth of an inch less in diameter than the interior diameter of the tube. The coating material will be distributed uniformly upon the inner surface of the tube after the plug 21 has advanced a short distance, providing a protective coating 28 therefor. lVhen the plug 21 first starts to more inlUt) ll l

wardly of the tube 2, the coating material or composition 0 is at the lower portion of the tube, as in Figure 1.3, so that the. coating 28 at the lower end portion of the tube from which the plug 21 is shot or projected, will extend nearer the end of the tube than the coating at the upper portion thereof, as in Figure 14.

The movement of plug 21 toward plug 1 causes the coatingmaterial c, with the exception of that which is applied to the interior surface of the tube 2 during this initial travel of the coating plug, to collect bet-ween this p ug and the plug 1 until the space between these two plugs is completely filled. as in Figure 14. The motion of plug 21 is then transmitted through this column of liquid to the reservoir plug 1 so that the two pln gs and the liquid confined therebetween travel through the tube at high speed. During this travel of the plugs through the tube a certain amount of the composition 0 flows about plug 21 and is distributed thereby uniformly over the interior surface of the tube 2. In this connection, it is to be noted that the plug 21 travels through the tube at high speed and the tapered nose 21a serves to exert outward pressure on the column of composition placed between the two plugs, this pressure being transmit-ted radially of-the tube so that the coating is applied to the inner surface thereof under pressure, the body of the plug acting to smooth the coating and to impart a uniform thickness thereto. As the plugs travel through the tube 2 the amount ofcomposition 0 between the two plugs diminishes continuously with the result that the coating plug 21 travels at a somewhat faster rate than the reservoir plug 1 and continuously gains thereon. By the time the plug 1 reaches the other end of the tube the composition 0 between the two plugs has been exhausted with the exception of a slight quantity thereof about the nose 21a of plug 21., and nose 21a. is, at this time, in contact with plug 1, as illustrated in Figure 15.

This remaining small quantity of composition c isuniformly distributed over the inner surface of the tube 2 to the end there. of. both of the plugs being discharged from the tube'at the opposite end thereof from which they are inserted into the tube. lreferably I provide a sufficient quantity of the composition c to have a slight excess over that required to coat the interior of the tube, this being to assure proper coating of the tube and to allow for any unusual conditions thereof. As the plug 21 is shot through the tube 2 at high speed it is possible, by this method, to coat the interior surface of the tube much faster than is possible by the use of brushes or similar devices. Also, the coating applied to the tube is of uniform thickness and hasla smooth finish,

both of which are highly desirable in coatbrush inserted into the same.

ing tubes. In Figure 16 I have illustrated, in axial section, a tube the interior surface of which has been coated in accordance with my invention, the slight excess of coating material being indicated as dripping from the end of the tube. As will be noted from this figure, the tube is uncoated for a short distance from the end thereof from which the coating plug is shot or projected through the tube. This short length of the tube can be readily coated by hand by a suitable This takes but a short time and the entire interior of the tube can, by my method, be coated with a uniform layer of protective composition in a fraction of the time required to apply such a coating to the interior surfaces of tubes by brushes or equivalent means.

It is practicable to coat the inner surface of the tube by placing the coating composition therein and then shooting the coating plug 21 through the tube in the manner described, omitting the reservoir plug 1. Under such conditions, during travel of the plug 21 through the tube, the coating composition 0 would be piled up in front of the plug 1 by the action thereof so as to provide, in effect, a liquid column in advance of the plug such as that shown in Figure 14. During travel of the plug 21 through the tube, the liquid of this column would be spread uniformlyover the interior surface of the plug, as before. Under ordinary conditions, however, I prefer to employ the reservoir plug 1 as creating a desirable back pressure and assuring uniform distribution of the coating composition over the interior of thetube. The provision of this reservoir plug also has the advantage of reducing to a minimum the portion of the tube which has to be coated by hand. I also contemplate the provision of means whereby the coating plug 21 maybe projected or shot into the tube from a point exterior thereof in such manner as to effectively coat the interior of the tube for the entire length thereof. thus obviating all necessity for any band coating of the tube.

It is desirable that means he provided whereby the thickness of the coating applied to the interior of the tube can be varied as required. I have, therefore, provided coating plugs of several forms such that the thickness of the coating applied to the tube will vary in accordance with the particular form of plug used. In Figure 3 I have illustrated a plug for applying a coating of minimum thickness.

This plug is, in its broader aspects, similar to the plug 21 but is flared slightly at its base end 29a, the body portion 29 being cylindrical and the nose 2% being rounded and somewhat longer than the nose of plug 21. The plug illustrated in Figure 4: is similar to that of Figure 3 but is provided with tube than the plug of Figure 3. The plug" 21 has a cylindrical body of uniform diameter without any flare at its base, and this plug applies a coating of medium thickness to the inner surface of the tube. a

In Figure 5 I have illustrated a plug similar to the plug 21 except that it is provided with two circumferential grooves 31. These grooves serve to retain a portion of the composition through which the plug passes in traveling through the tube and this form of plug applies a somewhat thicker coating to the tube than plug 21. The plug illustrated in Figures 6 and 7 is similar to that of Figure .5 except that the grooves 31 are connected by grooves 32 extending lengthwise of the plug, and grooves 33 extend lengthwise of the nose portion of the plug and open I into the first groove 31. These grooves permit the coating material or composition to flow into the grooves 31 with but little resistance with'the result that this form of plug applies a somewhat thicker coating to the tube than the plug of Figure 5. As will be noted more clearly from Figure 7, the grooves 32 and 33 are arranged in staggered relation, such arrangement being the most effective.

The form of plug shown in Figure 8- is similar to that of Figures 6 and 7 except that a third groove 31a is provided so that i the nose portion 34 is somewhat shorter and rounder than the nose of the plug of Figures 6 and 7. This form of plug is provided with the lengthwise grooves 35 in the nose opening into groove 31a, and the grooves 32 and 32a connecting the grooves 31 and 31a. This form of plug applies a heavier coating of ma. terial to the interior of the tube than the plug of Figures 6 and 7, and is intended to apply the thickest practicable coating to the tube. Under ordinary conditions, I prefer to use the plug illustrated in Figures 12 to 15, which applies a coating of medium thickness to the tube.

While I have illustrated and described my invention as used for coating the interior of a straight tube, for convenience of illustration, it is well adapted also for coating curved tubes since the plugs used will readily pass about curves of relatively short radius. Though my invention is particularly well adapted for coating small tubes which cannot be coated to advantage with brushes or equivalent means, I do not limit it to the use of small tubes since, by employing plugs of suitable size, tubes of relatively large diameters can be readily coated. In fact, there are many instances in which my invention can be used to advantage in coating tubes of larger diameters rather than coating the interior of such tubes by brushes or like means.

What I claim is:

1. A plug for use in coating the interior surfaces of tubes, said plug tapering toward one end and substantially conformin in size and shape to the interior of the tu e to be coated,-the plug being provided with a recess extending from its other end.

2. A plug for use in coating the interior surfaces of tubes, said plug being of substan tially cylindrical shape and tapering toward one end, the other end portion of the plug being flared. 3. A plug for use in coating the interior surfaces of tubes, said plug being of substantially cylindrical shape and tapering toward one end, the other end portion of the plug being flared, said plug being formed of highly elastic material.

4. A plug for use in coating the interior surfaces of tubes, said plug being of substantially cylindrical shape and tapering toward one end, the other end portion of the plug being flared and having a recess therein of appreciable area, said plug being formed of highly elastic material.

5. A plug for use in coating the interior surfaces of tubes, said plug being of substantially cylindrical shape and tapering toward one end, the plug being formed of highly elastic material. I

6. In combination in means for distributing a liquid upon the interior surface of a tube for coating the same, a reservoir plug conforming in size and shape to the interior of the tube and providing a snug closure therefor, and a coating plug fitting within the tube and tapering toward the reservoir plug, the base of said coating plug being yieldable, the two plugs cooperating with each other and with the intervening portion of the tube to form a reservoir for reception of the coating liquid and the coating plug acting to distribute the liquid over the interior of the tube during travel of the plugs and the liquid therebetween through the tube under pressure applied to the outer end of the coating plug.

7. In combination iii-means for distributing a liquid upon the interior surface of a tube for coating the same, a reservoir plug conforming in size and shape to the interior of the tube and providing a snug closure therefor, and a coating plug fitting within the tube, the end of the coating plug toward the reservoir plug being of less cross-area than the interior of the tube and the other end portion of the coating plug being elastic, the two plugs forming with the intervening portion of the tube, a reservoir for the coating liquid and the coating plug acting to distribute said liquid over the interior surface of the tube during movement of the plugs and liquid therethrough under pressure applied to the outer end of the coating plug.

8. The method of coating theinterior surfaces of tubes, consisting in placing a coating liquid within the tube, and then projecting a tapered plug through the tube, the plug tapering toward its leading end and the base end of the plug being yieldable and of approximately the same cross area as the interior of the tube.

9. The method of coating the interior surfaces of tubes, consisting in placing a quantity of a coating liquid in the tube, and then distributing such liquid over the interior surface of the tube by projecting a tapered plug of elastic material therethrough.

In witness whereof, I hereunto subscribe my name this 21st day of December, 1928.

' CHARLES F. MOORE. 

